1. Field of the Invention
The present invention relates to inductances made in monolithic form and comprising turns formed by metal tracks of several metallization levels.
2. Discussion of the Related Art
To obtain an inductive component having the highest possible inductance while exhibiting a reduced bulk, a possibility is to stack up the inductance turns which then comprise metal tracks of different metallization levels. However, as compared with an inductance having its turns formed by one or several metal tracks of a single metallization level, significant parasitic capacitive couplings between adjacent metal tracks of different metallization levels can be observed for an inductance having its turns formed by metal tracks of several different metallization levels.
Indeed, to decrease as much as possible the inductance bulk, it may be impossible to avoid for two turns formed by successive metallization level tracks, or possibly separated by an intermediary metallization level, to be substantially aligned with respect to one another. For conventional CMOS integrated circuit manufacturing processes, the metal tracks generally have thicknesses on the order of from a few tenths of a micrometer to one micrometer for a width of a few micrometers. As compared with adjacent metal tracks of the same metallization level, the opposite surfaces of aligned metal tracks of different metallization levels are larger. Further, the insulating material thickness separating two aligned metal tracks of successive metallization levels is on the order of a few tenths of a micrometer. For two aligned metal tracks of two distinct metallization levels separated by a single intermediary metallization level, the insulating material thickness separating the two tracks can reach 1 or 2 micrometers. The parasitic capacitive couplings between aligned tracks of different metallization levels can thus be greater than the parasitic capacitive couplings between adjacent tracks of the same metallization level and cause a strong degradation of the inductance performances.